DESCRIPTION: (adapted from Investigator?s abstract) Youth aggression and delinquency are serious problems with far-reaching effects on individuals and society. Recently, group interventions in which high-risk youths are taught psychosocial skills have resulted in improved youth behavior. However, common professional lore holds that aggregating antisocial youths in treatment groups is contraindicated due to opportunities provided for powerful processes of peer modeling and reinforcement of deviancy. This belief in negative iatrogenic effects of aggregating high-risk youths in group treatment persists, despite the fact that only one intervention study has found modest, indirect support for it and no studies have directly tested it. The present study will use a 2 (Treatment: skills training/attention-placebo) x 2 (Group Composition: only deviant/prosocial and deviant) between-participants design to test treatment processes and outcomes for high-risk youth. Adolescents will be randomly assigned to conditions, then participate in 12 weekly two-hour group sessions, which will be videotaped. Intervention process variables (modeling and reinforcement of deviancy and prosocial behavior) will be coded from videotapes. Treatment outcome variables (school adjustment and child-, parent-, and teacher-rated social skills and externalizing behavior) will be assessed pre-intervention, post-intervention, and six months following post-intervention. The most central hypothesis is that the mixed, or integrated, skills-training condition will be characterized by more positive intervention processes, mediating more positive treatment effects on high-risk youth than all other conditions.